As one of the routine works in the weather observation, various kinds of the weather elements such as the wind direction, the wind velocity, the temperature, the humidity, the atmospheric pressure and so on at each altitude from the ground up to the upper air are measured by means of an observation instrument provided hanging below the balloon freed in the air, whereby the signals (electrical codes) representing the results of the measurement are sent to a receiving station on the ground by means of a microwave. It is known that such a transmitter as hangs below the balloon is called radiosonde.
It is essential for a radiosonde to operate since the balloon with the radiosonde is freed on the ground (the sea) till it reaches the altitude of about 30 km, whereby the ambient conditions, being quite different from the ambient condition for our life on the ground, are remarkably severe, for example, the temperature covering from +40.degree. C.about.-80.degree. C, the atmospheric pressure covering from 1040 mb - 1 mb and the humidity covering from 1 % - 100 %, the radiosonde itself being subject to the vibration and the shock during the flight.
Further it is difficult to recover the radiosonde after the flight is over so that it is expendable.
From the above mentioned reasons it is required that the instruments for a radiosonde should be compact, light, cheap and stable in the characteristics even under the above mentioned severe physical and chemical ambient conditions over a wide range.
On the other hand, the time interval during which the characteristics should be stable is at longest several hours, till the termination of one flight observation.
In consequence it is necessary to manufacture the microwave oscillator for radiosonde, taking into consideration the requests quite different from those for the microwave oscillator used for the stationary transmitting station on the ground.
In case of radiosonde, so far the frequency from 1.6 GHz - 2 GHz has been used internationally, whereby as oscillation active element for the above mentioned frequency band a vacuum tube of special shape, so called penciltube has been used, while quite recently it is tried to substitute the above mentioned oscillation active element with what makes use of a transistor (generally a semi-conductive element) in view of the above mentioned various requests.
So far several simple microwave oscillator with a transistor suited for radiosonde covering from 1.6 GHz to 2 GHz have already been proposed.
FIG. 1 shows a circuit diagram of a representative microwave oscillator which has been proposed. In case of the microwave oscillator with the circuit as is shown in FIG. 1, the part shown with a figure L in the drawing is composed a two dimensional micro-stripline formed with a conductor sheet on a dielectric body (insulation body). Although the construction of an oscillator using a micro-stripline on the base plate of a dielectric material is simple, it is essential that the loss in the microwave band of the material for the base plate be small while its temperature characteristics is superior. A base plate of dielectric material which fulfills the above mentioned characteristics is so expensive that it is not desirable to apply such an expensive material to the microwave oscillator of radiosonde, article of consumption.
Apart from the above as an oscillator with stable oscillation frequency, there is an oscillation circuit consisting of a coaxial resonator and a semi-conductor element. However, in case of an oscillator with coaxial resonator it is essential to improve the characteristics of the coaxial resonator, whereby the construction is complicated so that it is not suited for radiosonde due to the larger dimension, the higher price and the larger weight.
The present invention is made in consideration of the above mentioned various problems.
A purpose of the present invention is to offer a compact and light microwave oscillator suited for a radiosonde.
Another purpose of the present invention is to offer a microwave oscillator consisting of a cheap and conventional base plate material and suited for a radiosonde.
Further another purpose of the present invention is to offer a microwave oscillator consisting of cheap and conventional materials beside the base plate and suited for a radiosonde.
Further another purpose of the present invention is to offer a microwave oscillator which is capable of keeping the necessary characteristics for the observation of the weather element under the severe ambient conditions during the flight of the radiosonde.
Further another purpose of the present invention is to offer a microwave oscillator which can be manufactured so easily as to contribute much to reduce the price of radiosonde.
Further another purpose of the present invention is to offer a consumable microwave oscillator suited for radiosonde.